I did not get a reply or information about using brew head or group head temperature. It may be a good temperature place to tell if the machine is ready to brew, especially if you use the steam switch to help. A brew head temperature of say 200F that would hold there may mean that the machine is ready and stable, even if you get there in 5 minutes. My brew head/portafilter sandwich temperature is about 200F when I am ready. I slipped a K thermocouple into the PF notch and groove. I have now moved the PID set to 212F to get 200 – 201 with 30 minutes to warm up.

I made a thermofilter and have checked the temperatures using the alarm function to hold intra-shot temperature and to give quick recovery. I can do three 25 second doubles of about 50 ml with 1 minute between and get brew temperatures of 199 – 201F fairly consistently. I have found that the largest variable is water volume. The heater runs to alarm set temperature, off at 255F and back on at 254F activated with the brew switch. When the brew switch goes off, it settles toward 212F, idle PID. I also tried once at 1.5 minutes rest and it seemed ok, so, rest may be need for 1 minute to equilibrate and mix cool water with heat, and then the PID holds temperature. The PID is not back to 212F at 1 minute however, but low 220F’s. That is in PID range, so PID is trying to damp out over/under shoots.

I made a silent movie, old school since I did not want to narrate. Video is worth a thousand words.

I have used the system for about 2 weeks and have been pleased. I have tried a double, and then a second double in about 1 – 1.5 minutes, how ever long it takes me to be ready, several times. Mostly, I normally just pull a double once in the morning, and another later in the day. I wanted to test the system. The thermofilter test worked fine, in fact I could gain temperature intrashot if not careful, or if too small of a volume for the double, noted above. In the real world of taste, the system works fine also. Not bitter or sour on the second double, so the temperature is acceptable.

I use the steam switch for about 3 seconds and then wait 3 seconds before the first double, and then no more manipulation. The reason for the initial steam switch is for timing of heat, not amount. It takes some time to get heat into the water. The initial 3 seconds heat and then rest will get the heat ahead of the cool water and blunt the expected intrashot drop, and then the alarm function of the PID will hold or raise the temperature.

The small boiler of the Gaggia and high wattage will allow the Gaggia to react very quickly. Only the PID and alarm functions are used. I am not using any coil or preheat, though preheat may make the system a little less critical of water volume by having less temperature fluctuation. Trouble is, if I calculate correctly, the volume of 1/4” tubing is about 9 – 10 ml per running foot. The preheat temperature could change with a second or third double and that would be difficult to compensate. The current system is essentially electronic and reversible. All PID and electrical connectors are slip on/spade.

This can all be done manually with use of the steam switch without electronics if you learn that method, well demonstrated by AndyP.

I still have some curiosity about monitoring water temperature with a probe into the boiler, or group head temperature with a sensor drilled into the brass head of the boiler. Feel free to post info about that if you have done it or find a thread/post.

I got a chance to recalibrate the whole system. I made another thermofilter, see thermofilter thread above. The thermofilter was about $20 including basket, not including sensor and reader which could be an $8 Polder digital thermometer.

I basically got the same results. I managed a 50 ml 25 second flow and did a repeat of the prior testing. Essentially the same findings. A first pull is preceded by about 4 seconds of steam switch and 4 seconds rest to get heat in the system. The PID alarm function then adds heat and will keep the temperature to 199 - 200F, depending on the alarm setting. As before, you can add too much heat and get an intrashot raise, or too little and get a little drop.

The thermofilter is a great learning tool even without a PID. You can learn how to temperature surf and how much heat/steam switch to add to hold temperature during the shot.

Here is some common PID, alarm, and SSR wiring. Though it is Gaggia related, it is simialar to Rancilio Silvia PID wiring. Specific wiring diagrams would need to be applied to each machine and brand. This section provides a link to the Silvia PID thread, and is from discussion with tasseloff.

A few comments about wiring. The Skene diagram diodes are IN4001 or 1N4001, but there are others that work as well. They can be cheap as they are just blocking diodes with low voltage and amperage requirements.

I have used IN5400 and NTE5800 in the same place. Use an equivalent catalogue or ask at your electronic supply place.

I believe the Skene diagram incorrectly shows the "ground" to PID 1. My Gaggia does not use ground, and if used, I believe it is PID 3.

A picture is worth a thousand words, so included. I use small shrink tubing that will just fit over the spade solder/crimp end. The 24 or 26 awg is small and I wanted shrink to grasp it. On one female spade I show larger unshrunk shrink tubing that just fits over the 1/4 female spade. I shrink that on over the fitting and small shrink. Insolate everything.

The diodes have long solder ends. I clip those to about 3/8" and solder my 26g wire and again over shrink. The diode solder end in a great conductor of heat, do not destroy the diode. I show a clamp that I clamp on to help hold, and heatsink. I smoothed the teeth out of the clamp and can use it to even grip small wires. Teeth can pinch through the wires. Some put on shrink overwrap, but then no heatsink.

I used this in a removable portion of my machine while testing, but it is similar to what I have at the SSR. I have a small ring connector in place of the single male spade. I now have 3 diodes to the SSR, not 2.

A few more comments on PID wiring. The brew side is straight forward and easily found on search. I had a little more difficulty figuring out the steam side and how it worked with an AC-DC voltage supply vs. a 9v battery. I will briefly explain in case there are others who have not understood.

On Classic, and perhaps Silvia, the steam switch has 2 separate functions. One side of the steam switch controls the 3 way and the other side controls the ‘stats. In particular on Classic, the stat side causes the brew stat to be bypassed so that it does not stop the steam stat from having control. With a PID the brew stat is the PID and can go to any desired temperature. If you set it over t-stat temperature then the t-stat will break the circuit. I pulled the wires on that side of the switch leaving the 3-way controlled normally. If you pull both of the wires on the stat side of the steam switch, then you can use that side for AC or DC. AC can turn on a AC-DC charger and DC can control a battery circuit. That goes to PID alarm and SSR, the Skene diagram.

I had always meant to fill in the "how to" of Gaggia PID wiring. Not terribly difficult to figure, but nice to know even before you get the PID and instructions. You can collect supplies and make the wires even before you acquire the PID, or while waiting for shipping.

A little more on PID wiring 101 level, for DIY. You will need a few wire sets and a way to keep them straight. You could use multiple colors, but if you went out and purchased wires, then one color is likely. All wires adequately insulated and connected, solder or crimped. You will be mixing water and electricity, at least in the same container/machine.

I set of 14 awg high temperature load wires between SSR and stat wires. You are replacing the B-stat which has 2 male spades. I used ring connectors at the SSR end and female spades at the B-stat wire end.

Assumed that the SSR is screw in connectors that will use ring connectors, or clamp wire.

I used about 2’ lengths (24 or 26 awg), and on Gaggia that was a little long, easy enough to coil.

Pair 1) PID Power wires with piggyback at one end and bare at the other. Tape with a small piece of tape to identify as PID Power. You will piggyback to the front “power on” switch and to the incoming opposite leg at the back plug

Pair 2) PID to SSR wires, bare PID end and ring connector or bare at the SSR end. Mark the pair and decide the positive and put in a diode at the SSR end, note diode direction.

Pair 3) Wires from the power supply, or battery, to the SSR. The Positive side goes up to the PID, and then back to SSR positive. You manually switch this wire with the steam switch, or in my case on here with the brew switch, and then activate the alarm circuit. The alarm circuit in the PID is always trying to drive the SSR, but has no circuit until you activate the switch. This wire needs a diode at the SSR and connects with the PID SSR output positive wire like the Skene diagram. Also looks somewhat like the shortened version shown a couple posts above. The negative side goes over to the SSR, or to the negative side SSR wire, input side. The negative wire will usually end up being short, but the positive side goes to the PID and back to the SSR. You can shorten the Negative side wire and add to the Positive side, perhaps from the PID out to the SSR.

Pair 4) The Sensor wires, sensor or thermocouple to PID

You may need a ground wire depending on machine.

Option pair) Repeat similar to pair above if you choose to use all 3 functions.

High temperature 26 – 22 awg stranded wire for non-load connections. I like the 26 or 24 as the wire get bundled in to the back of the PID. Larger is more difficult to work with in the bundle. NTE stranded 105C wire, or surplus PTFE mil_spec wire like here

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